Centrifugal grinding mill



March 27, 1928.

W. A. GIBSON ET AL CENTRIFUGAL GRINDING MILL Filed June 22. 1925 2 Sheets-Sheet 1 Fig. 1.

z 7 Q 1 4 1 1/ A WWW lnvanior's. William A..G'|bs0n domes urKe b ym Afiys.

March 27, 1928. 1,663,881

. v w. A. GIBSON ET AL CENTRIFUGAL GRINDING MILL Filed June 22. 1925 2 Sheets-Sheet 3 lnvenTors.

WiHiumA.Gibson James G. BurK b flwzwwimt A TTy s.

Patented Mar. 27, 1928.

" UNITED STATES I 1,663,881 PATENT OFFICE.

WILLIAM A. GIBSON AND JAMES G. BURKE, OF ALLENTOWN, PENNSYLVANIA, AS-

SIGNORS 'IO BRADLEY PULVERIZER COMPANY, OF ALLENTOWN, PENNSYLVANIA,

A CORPORATION OF MAINE.

CENTRIFUGAL GRINDING KILL.

Application filed June 22, 1925. Serial m. 88,676.

This invention relates to improvements in grinding mills of the centrifugal type which comprises a horizontal grinding ring or die and a central shaft which actuates one or more movable grinding members which, during the rotation of the shaft, are caused by centrifugal force to co-operate with the grinding ring or die and crush the material therebetween.

Certain mills of this type are provided with an air separation chamber located above the grinding ring. The finely pulverized material is drawn from this chamber through a conduit leading into the upper portion thereof to a suction fan which discharges the air laden with the fine material into a collector usually of the cyclone type which separates the finely ground material from the air, the air usually being returned to the grinding chamber below the grinding ring. Inasmuch as the particular type of separating means forms no part of the invention and is well known it is not illus'-' trated or specifically described herein.

In usual types of grinding mills the air is admitted below the grinding ring and. the suction of the fan leading to the air separator lifts a considerable amount of relatively coarse material from the grinding pan and discharges it into the separator.

Experience has demonstrated that in mills in which air separation of this character is not'employed the finely ground material rises above the grinding ring. One of the objects of the present invention is to provide means which will permit the suction to carry away the finely ground material which thus rises above the grinding ring without substantially affecting the coarser material in the grinding pan or in the lower portion of the grinding chamber. This is accomplished by providing means for admitting air into the grinding mill above the grinding ring and preferably in proximity thereto instead of below the grinding ring.

A further object of the invention is to provide means for directing the current or currents of air admitted to the grinding mill in selectively different directions with respect to the radius of the grinding mill. It has been found that when the current is directed substantially radially into themill a substantially direct upwarddraft' is pr duced which carries away relatively coarse material as well as the finely ground material, whereas if the air is admitted tangentially the heavier material is thrown toward the periphery of the chamber and the finer material alone drawn out by the suction fan.

The present invention comprises adjustable means for directing the current or currents of air which are admitted into the grinding mill in any desired direction relatively to the radius of the chamber, thus enabling the character of material which is delivered to the air separator to be accurately controlled. This is accomplished by providin an annular chamber for the air to be a. mitted surrounding the mill, preferably directly above the grinding ring, and providing a series of adjustable vanes for directing the entry of air in the manner above described.

A further feature of the invention consists in providing adjusting means which will prevent the escape of air from the air inlet chamber when the vanes are in any position of adjustment.

Another object of the invention is to provide a novel means for feeding material to the grinding rolls. In previous constructions a hopper has been carried by the roll I supporting spider into which the material is charged and from which it is delivered through suitable chutes in front of the grinding rolls. In previous constructions the material which is supplied to the mill, being'of an abrasive character, rapidly Wears the bottom and walls of the hopper and also the chutes which deliver it in the path of the grinding rolls.

In the presentinvention the distributing hopper is; located axially above the central roll actuating shaft and the material is delivered to the distributing hopper as nearly as possible in the line of the axis of the shaft. By thus delivering the material to the distributing hopper the incoming abrasive material is progressively piled'up upon other material resting in the bottom of the hopper and as it slides from the sides of the conical ile thus produced it passes down through the chutes to the-rolls with relatively little abrasive action upon the walls of the hopper and chute.

vide a novel means for securing the grind-' ing ring or die in its seat which will permit 1 the die to be more easily removed and will also permit the die to expand and contract under variations of temperature. This is ac-- complished by providing a plurality of spring clamps for holding the die in place. It not only enables the dies readily to be removed and also permits expansion and contraction of the die, but requires no adjustment when once placed in commission, there by eliminating the above and numerous other objections which are found when usualwedges are employed for retaining the die in place.

These and other objects and features of the invention will more fully appear from the followingdescription and the accompanying drawings and will be particularly pointed out in the claims. i 1 A' rinding mill of the centrifugal type embo ying the invention is illustrated in the accompanying drawings, in which,-

Fig. 1 is a vertical diametrical section of a centrifugal grinding mill having an air separating chamber located above the grinding chamber and embodying the features of the invention;

Fig. 2 is a detail plan view-of the section of the air inlet conduit showing the adjustable vanes for directing the incoming air in selectively diflerent directions with respect to the radii of the grinding mill chamber; also illustrating a preferred means for accomplishing the adjustment;

Fig. 3 is a detail view, partly in section,- showing the manner in which the vanes are mounted and adjusted; and,

Fig. 4 is a plan view of hopper illustrated in Fig. 1.

The grinding mill illustrated in the drawings comprises a metallic base or bed 1 of the I distributing general annular form having a wide hori-' zontal peripheral flange 2 which rests upon a suitable foundation 3. A central hollow standard 4 having an enlarged disk-like foot or base 5 is secured to the bed and forms the bottom of the grinding chamber 6. The inner face of the wall of the bed 1 is provided with an annular recess which receives a grinding ring guide 7 having a downwardly and inwardly tapered face and the grinding ring 8 is provided with an outer peripheral face complementary to the face of the grinding ring guide 7.

Resilient means are provided for retaining the grinding ring in its position. The preferred means which is illustrated herein comprises a plurality of stiff, spring clamp ing plates or levers 9 having downwardly extending flanged ends 10 and 11, the outer flange 10 resting upon the top face 12 of the bed, while the other flanged end 11 rests upon the top of the grinding ring 8. A bolt 13 having a wedge-shaped end 14 anchored in a complementary socket extending from the inner wall of the upper portion of the bed l'passes through the lever 9 preferably about midway of its ends. A suitable nut or nuts 15 upon the anchoring bolt 13 serves to force the ends of the lever firmly against the upper faces ofthe bed and grinding ring with suflicient force to retain the grind: ing ring in place and yet providing sufficient resilience to permit expansion'and contraction of the grinding ring while retaining the same firmly in place.

When it is desired -to remove the grinding ring the levers 9 can be readily removed by unscrewing the nuts 15 and the grinding ring can then be lifted from its seat. By reason of this construction a eat deal of time is saved in assembling an dismantling the grinding ring.

The rollers 16, which co-operatewith the grinding ring 8, are carried upon the lower ends of shafts 17 which are fixedly secured at their upper ends in rocker heads 18 pivotally mounted upon stud shafts 19 which extend across arms 20 of a spider 21 which is fixedly secured upon the upper end of the roll actuating shaft 22. The roll actuating shaft extends vertically upwardly through the standard 1 and desirably is provided near its upper end with an antifriction hearing 23 located near the upper end of the post and also with an anti-friction bearing 24: located at the lower end of the standard 4.

Desirably interengaging annular members 25 and 26, located upon the spider and upper end of the standard respectively, serve to exclude dust from the upper hearing between the shaft and the standard, and lubri shaft 31 which is actuated in any suitable manner. The hub of the gear 28 is supported by a thrust bearing upon the central portion 32 of a gear casing 33 of substantially annular form which is secured to the under face of the bed 1.

As illustrated herein the thrust bearing comprises flat wear plates 34 which rest upon a plate 35 having a lower spheroidal face which in turn rests upon a complementary face of a lower bearing member 36 which in turn rests upon the central portion of the gear casing. A flange 37 extends upwardly from the central portion of the gear casing and closely surrounds the shaft, a suitable packing member being provided to exclude gear lubricant from this bearing. The driving shaft 31 is journalled in a suitable bearingin a bracket 38 the upper face 39 of which is secured to the bed plate and the flange 40 of which is secured to the gear casing. c

It is obvious that the rotation of the driving shaft will cause the pinion 30 to rotate the gear 28 thus rotating the roll actuating shaft 4 with the spider 21 which is mounted upon the upper end of it, thereby causing the centrifugal rolls 16 to rotate about the axis of the shaft 32 so that centrifugal force will cause these suspended rolls to co-operate with the annular die.

Another feature of the invention, as above stated, consists in providing novel means for feeding the material to be ground to the rolls. In the construction illustrated herein the material is fed into a suitable chute 41 externally of the mill which leads to a horizontal screw conveyer 42 the end of which is located in such a position as to deliver the material into a distributing hopper 43 the central portion of which is mounted directly over the axis of the shaft 22. The hopper desirably is of a substantially trefoil construction as illustrated in Fig. 4 having a central circular base 44 provided with a downwardly extending flange 45 which surrounds the nut 46 on the shaft 44 which secures the spider 21 to the shaft. The hopper has a downwardly tapering wall 47 with three lateral and downwardly extending tubular sections 48 which lead respectively to chutes 49 the lower ends of which are located in advance of the respective rolls so that the material is delivered by the centrifugal force of rotation of the hopper continuously in front of the respective rolls.

The spider 21 desirably is provided with extensions 50 to which substantially vertical arms 51 are secured which carry plows 52 located near the bottom of the grinding pan and in-front of the rolls and act to throw the material in the pan upwardly into'the path of the roll-s.

By reason of the hopper construction above described the material fed into the mill by the screw conveyer is deposited upon the bottom of the hopper in a conical pile the axis of which is substantially coincident with the axis of the vertical roll actuating shaft 4 and the material is delivered from the periphery of this pile by the action of gravity and centrifugal force through the downward extensions of the hopper and chutes 49 to the rolls with a minimum abrasive action upon the walls of the hopper and chute.

The principal feature of the invention consists in providing novel means for admit ting air into the chamber of the mill in such a manner that the suction of the air separating means will more effectively remove the finest material from the grinding chamber and in also providing means for directing the incoming air selectively in predetermined paths relatively to the radius of the grinding chamber so that the degree of fineness of the material which is drawn from the grinding rounded by spacing sleeves 54 which support an annular plate 55, the plate being clamped firmly upon the sleeves by nuts 56 upon the screw threadedupper ends of the posts 53. A series of vanes 57 having tubular hubs 58 are pivotally mounted upon the sleeves 54 which surround the posts. Each of these vanes is provided with a lateral offset arm or lug 59 having seated therein a vertical bolt 60 which passes through an angularly disposed arcuate slot 61 in the upper wall 62 of a preferably substantially rectangular conduit 63, which surrounds the grinding mill mainly above the bed 1 and of which the flange 2 of the bed may form the base. The arcs 61 are concentric with the axes of the vertical posts 53. An annular adjustingring 64 is mounted'upon the upper wall 62 of the conduit and is provided with angularly disposed slots 65 through which the bolts 60 pass. The upper ends of the bolts 60 are provided with washers 66 and nuts 67 which hold the adjusting plate 64 in place, but permit rotative movement thereo The slots 61 and 65 are located in angular relation to each other so that the rotative movement of the adjusting ring 64 will move the bolts 60 and arms 59 and the vanes to which they are attached pivotally about the axes of the vertical posts 53. Thus thevanes may be adjusted in any desired direction relatively to radii of the grinding mill chamber. The relative angular arrangement of the slots 61 and 65 is such that the plates 62 and 64 respectively overlie all portions of the slots 65 and 61 except the registering portions through which the bolts 60 pass, thus preventing escape of the air from the inlet conduit.

Air may be admitted to the conduit 63 from the return conduit of the suction fan (not shown) in any suitable manner as will be readily understood by those skilled in the art. A preferably annular casing- 68 is mounted uponthe annular plate 55 and is provided with a conoidal top or cover 69 through the central upper portion of which extends the lower end of the conduit 70 which leads to the air separating means (not shown).

' In the operation of the mill thematerial fed to the grinding chamber is finely pulverized by the co-operating action of the centrifugal rolls 16 and the annular die with which they co-operate. The finely ground material rises above the plane of the grinding mill into the path of the currents of air which are admitted from the annular conduit surrounding the grindin mill immediately above the die. This ely ground material is thereby carried upwardly by the draft of the suction fan and delivered into the separator. B adjusting the position of the vanes relatively to radii'of the grinding mill chamber materials of diflerent minimum degrees of fineness may be with drawn from the grinding chamber. When the vanes are so positioned as to direct the entering air currents in a substantially radial direction the draft caused by the suctionfan is almost directly upward, while as the vanes are adjusted to direct the incoming air currents more tangentially the heavier particles of material which are suspended in the air Will be thrown to the periphery of the grinding chamber and will drop againv into the bed and be reground. Thus adjustment may be made of the vanes which will control the degree of fineness of the material withdrawn from the mill by the air separating means.

Any suitable means may be provided for actuating the adjusting ring to produce the desired adjustment. As illustrated in Fig. 2 the adjusting ring 64 has secured to it an L- shaped bracket 71 into which a rod 7 2 is secured. The rod 7 2 may be connected at its opposite end to any suitable adjusting means for moving the rod lon 'tudinally and retaining it in its adjuste position. As numerous means for producin such adjustment are common in the art 1t has not been deemed necessary to illustrate any particular type herein.

It will be understood that the particular embodiment of the invention described here in is of an illustrative character and is not restrictive and that various changes in form, construction and arrangement of parts may be made within the spirit and scope of the following claims.

Having thus described the invention, what is claimed as new, and desired to be secured byLetters Patent, is:

1. In a centrifugal grinding mill comprising a grinding chamber having therein a horizontal annular grinding ring, co-operating centrifugally actuated grinding members and a superposed air separating chamber communicating with said grinding chamber, means for admitting air to said grinding mill above and substantially adjacent to the.

grinding ring and adjustable means operable selectively to direct the air thus admitted in different predetermined directions relatively to the radius of the grinding mill chamber and thereby to vary the character of the air currents within said se arating chamber and regulate the 'action 0 the air separator.

2. In a centrifu l inding mill comprising a grinding 0 am er having thereln a horizontal annular grinding ring, co-operating pivotally suspended centrifugally actuated grinding members and a casing located above said grinding chamber forming an air separating chamber, means located in proximity to said grinding chamber and below said separating chamber for admitting air to said mill having adjustable vanes operable selectively to direct the air thus admitted in different redetermined directions relatively to the ra ii of the grinding chamber and thereby to vary the character of the air currents within said separating chamber and regulate the action of the air separator.

3. In a centrifugal grinding machine comprising a base presenting an annular grinding chamber and having therein a horizontal annular grinding rin co-operating centrifugally actuated grin ing members, a series of posts mounted on said base in proximity to said grinding ring, a ring supported by said posts, a casing mounted upon said ring and forming an air separating chamber, a series of vanes pivotally mounted upon said posts and means for adjusting said vanes to direct the air enterin the mill in predetermined directions re atively to the radii of said grindin chamber.

4. In a centri ugal grinding machine comprising a base presenting an annular grind ing chamber and having therein a horizontal annular grinding ring, co-operating centrifugally actuated grinding members, a series of posts mounted on said base, a ring supported by said posts, a casing mounted upon said ring and forming an air separat ing chamber, a series of vanes pivotally mounted upon said posts, an inlet conduit surrounding said series of vanes and having a top wall provided with arcuate slots, arms on said vanes extending through said arcuate slots and means for simultaneously adjusting said arms in said arcuate slots, acting also to prevent escape of air from said inlet conduit.

5. In a centrifugal grinding machine com prising a base presenting an annular grinding chamber and having therein a horizontal annular grinding ring, co-operating centrifw ugally actuated grinding members, a series of posts mounted on said base, a ring supported by said posts, a casing mounted upon said ring and forming an air separating chamber, a series of vanes pivotally mounted upon said posts, an inlet conduit surrounding said series of vanes and having a top wall provided with arcuate slots, arms on said vanes extending through said arcuate slots and means for simultaneously adjusting said arms in said arcuate slots including a rotatable ring mounted upon the top Wall of said conduit and provided with slots extending in a direction oblique to the direction of said arcuate slots engaging the arms of said vanes and means for adjusting said ring.

6. In a centrifugal grinding machine comrising a base presenting an annular grind- 1ng chamber, a horizontal annular grinding ring mounted upon said base and resilient clamping means for retaining said grinding ring in position comprising a lever engaging at its ends respectively the upper face of said base and said grinding ring and a bolt secured to said base engaging the central portion of said lever and acting to press the ends thereof respectively firmly against said base and grinding ring.

In testimony whereof, we have signed our names to this specification.

WILLIAM A. GIBSON. JAMES G. BURKE. 

